Marijuana has economic benefits, but public health risks are undecided

The marijuana business is booming in the U.S. Medicinal marijuana is legal in 30 states and the District of Columbia. Eight states have legalized recreational marijuana. Ballot initiatives yesterday added Michigan and Missouri to the legal recreational and medicinal states, respectively. Sales figures are up wherever it is legally sold. In Colorado, for example, marijuana sales topped out at nearly $6B since 2014’s legalization. In 2017, sales there reached $1.5B and this year’s sales are on track to surpass that figure. This includes CBD (used medicinally, not the subject of this article) and plants with high levels of DTHC or THC, cannabis’s main psychoactive compound.

This is all excellent news for municipalities and states that benefit from increased tax revenues and for savvy marketers who now sell marijuana at the rate of alcohol. Unfortunately, marijuana’s public health risks are not as clearly understood as the risks of alcohol.

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The incredibly broad claims made about marijuana’s benefits, bear strong resemblance to the extravagant cure-all claims made for patent nostrums of the 19th century.

The LA Times recently reported that wild assertions — i.e., cannabis cures cancer — are widely believed. A common misperception is that marijuana comes from small growers, but in fact it’s several dozen publicly traded firms that grow the tons of marijuana produced every quarter. These big companies include Canada’s Canopy Growth Corp. (valued at $4.5B), Aurora Cannabis ($3.5B) and several American companies valued up to $500M.

Despite this, people see marijuana as a local, healthy product. A recent survey — Risks and Benefits of Marijuana Use — found that Americans view marijuana more favorably than evidence warrants. While 48 percent of American adults surveyed identified marijuana’s pain management benefits, a 2017 National Academies study found “insufficient evidence” to support cannabinoids for treating musculoskeletal pain and poor evidence that marijuana is effective in managing neuropathic pain.

A recent Lancet study found that patients who used cannabis reported more severe pain than those who did not. On the other hand, a National Academies review of the Health Effects of Cannabis and Cannabinoids found “substantial evidence” that cannabis is effective for some forms of chronic pain.

One certainty: marijuana’s impact on the developing brain. October’s American Journal of Psychiatry reports that marijuana may pose greater risk to teenagers’ brains than alcohol. Marijuana had "significant, "short and long-term impacts on four key cognitive areas: problem solving, long-term memory, short-term memory manipulation and the ability to stop a habitual behavior when needed. The study could not tie alcohol to these negative effects. Another recent study, found young people who used marijuana frequently did worse than non-users on memory tests, learning and higher-level thinking involving problem solving and processing information.

Marijuana is addictive. About 9 percent of adult users are affected, but teenagers have nearly double the chance of becoming addicted, more than 17 percent if they start as adolescents. The frequency of addiction appears to be increasing. More potent cannabis strains may be a factor and target marketing may help this along. Colorful THC gummies and pink- or rainbow-colored rolling papers indicate teens are an audience that marijuana entrepreneurs are targeting.

While research is still ongoing, emerging data suggests that childhood or infant exposure to marijuana may have a lasting impact on memory, executive function and even IQ. Between 2006 and 2013, the rate of marijuana exposure among children aged five and younger increased 148 percent. Moreover, the number of toddlers accidentally exposed increased every year from 2013 through 2016. In Colorado alone, rates of marijuana intoxication in young children increased 150 percent from 2014 to 2016. Half of these exposures involved legal, recreational marijuana.

According to a study led by Colorado pediatrician Dr. Sam Wang, emergency call rates for pediatric marijuana intoxication cases in decriminalized states increased by 30.3 percent per year; transitional states increased by 11.5 percent per year. Children in legal marijuana states had more severe symptoms and were more likely to be admitted to a critical care unit compared with those in states where marijuana was illegal. Correlating the frequency and dose of marijuana exposure of children with long-lived, adverse effects should be a research priority.

Finally, there’s drugged driving. The Pew Charitable Trusts reports that automobile deaths have spiked with the legalization of marijuana; 44 percent of fatally injured drivers tested for drugs had positive results in 2016, according to Governors Highway Safety Association data, up more than 50 percent from 2006. A study of drugged drivers in Washington (2010-2014) found the proportion of drivers in fatal crashes testing positive for THC increased after legalization. In 2014, the number and proportion of drivers in fatal crashes who were positive for THC were both more than double the averages from the prior four years.

Elected officials may not be well informed on these risks. With the wealth of misinformation circulating, public health authorities have a difficult task before them in educating decision makers on the downside of increased marijuana use due to legalization.

Public enthusiasm for cannabis — and the private sector’s desire to capitalize on it — has outstripped acknowledgement of the drug’s inherent problems which need to be better understood if legal marijuana will remain in the public interest. The need for good science to better inform the public and elected officials so that the right decisions can be made and precautionary measures put into place has never been greater.

Jonathan Fielding M.D., is a professor of public health and pediatrics at University of California, Los Angeles.